A transmit power control circuit, which can control a transmit power of a transmit power control circuit through wide dynamic range and can reduce an insertion loss. A first attenuator inputs a radio-frequency signal and outputs an output signal after controlling the inputted radio-frequency signal. A selective switch inputs the output signal of the first attenuator, and outputs it to one of a main transmission line and an auxiliary transmission line. One directional coupler is provided to the main transmission line and has one and another ends respectively connected to selective switches. The selective switches are switched by a signal from a microcomputer. When the selective switch is switched to the main transmission line, one end of the directional coupler is connected to a terminator, and another end thereof is connected to a wave detector. On the contrary, when the selective switch is switched to the auxiliary transmission line, one end of the directional coupler is connected to the auxiliary transmission line, and another end thereof is connected to a terminator.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A transmit power control circuit comprising: a variable gain circuit for inputting a radio-frequency signal, for amplifying the radio-frequency signal with a gain which changing based on an external control signal, and for outputting an amplified radio-frequency signal as an output signal; a first switching circuit for selecting one of a main transmission line and an auxiliary transmission line, and for outputting the output signal of the variable gain circuit to the one of the main transmission line and the auxiliary transmission line; an amplifying circuit provided to the main transmission line, and for amplifying the output signal of the variable gain circuit, which being outputted to the main transmission line; a directional coupler coupled with the main transmission line with a predetermined amount of coupling, and having one end and another end; a second switching circuit for connecting the one end of the directional coupler to a first terminator when the output signal of the variable gain circuit is outputted to the main transmission line, and for connecting the one end of the directional coupler to the auxiliary transmission line when the output signal of the variable gain circuit is outputted to the auxiliary transmission line; and a third switching circuit for connecting said another end of the directional coupler to a wave detector when the output signal of the variable gain circuit is outputted to the main transmission line, and for connecting said another end of the directional coupler to a second terminator when the output signal of the variable gain circuit is outputted to the auxiliary transmission line.
2. The circuit according to claim 1 , wherein the amplifying circuit includes an amplifier for amplifying by using a predetermined positive gain.
3. The circuit according to claim 2 , further comprising a power shutdown circuit for shutting down off a power supply to the amplifier, when the first switching circuit switches the selection from the main transmission line to the auxiliary transmission line.
4. The circuit according to claim 1 , wherein: the amplifying circuit includes an attenuator for amplifying the output signal of the variable gain circuit based on an another control signal, and an attenuation of the attenuator is controlled without changing a gain of the variable gain circuit when the output signal of the variable gain circuit is outputted to the main transmission line, and the attenuation of the variable gain circuit is controlled without changing the gain of the attenuator when the output signal of the variable gain circuit is outputted to the auxiliary transmission line.
5. The circuit according to claim 1 , wherein: the amplifying circuit includes a variable gain power amplifier whose gain changes based on the external control signal, a gain of the variable gain power amplifier is controlled without changing a gain of the variable gain circuit when the output signal of the variable gain circuit is outputted to the main transmission line, and the gain of the variable gain circuit is controlled without changing the gain of the variable gain power amplifier when the output signal of the variable gain circuit is outputted to the auxiliary transmission line.
6. A transmit power control circuit comprising: a variable gain circuit for inputting a radio-frequency signal, for amplifying the radio-frequency signal with a gain which changing based on an external control signal, and for outputting an amplified radio-frequency signal as an output signal; a first switching circuit for selecting one of a main transmission line and an auxiliary transmission line, and for outputting the output signal of the variable gain circuit to the one of the main transmission line and the auxiliary transmission line; an amplifying circuit provided to the main transmission line, and for amplifying the output signal of the variable gain circuit, which being outputted to the main transmission line; and a directional coupler coupled with the main transmission line with a predetermined amount of coupling, and having one end and another end; and a second switching circuit for connecting the one end of the directional coupler to a first terminator when the output signal of the variable gain circuit is outputted to the main transmission line, and for connecting the one end of the directional coupler to the auxiliary transmission line when the output signal of the variable gain circuit is outputted to the auxiliary transmission line.
7. A transmit power control circuit comprising: a variable gain circuit for inputting a radio-frequency signal, for amplifying the radio-frequency signal with a gain which changing based on an external control signal, and for outputting an amplified radio-frequency signal as an output signal; a first switching circuit for selecting one of a main transmission line and an auxiliary transmission line, and for outputting the output signal of the variable gain circuit to the one of the main transmission line and the auxiliary transmission line; an amplifying circuit provided to the main transmission line, and for amplifying the output signal of the variable gain circuit, which being outputted to the main transmission line; a directional coupler coupled with the main transmission line with a predetermined amount of coupling, and having one end and another end; and a second switching circuit for connecting said another end of the directional coupler to a wave detector when the output signal of the variable gain circuit is outputted to the main transmission line, and for connecting said another end of the directional coupler to a second terminator when the output signal of the variable gain circuit is outputted to the auxiliary transmission line.
8. A transmit power control circuit comprising: a variable gain circuit for inputting a radio-frequency signal, for amplifying the radio-frequency signal with a gain which changing based on an external control signal, and for outputting an amplified radio-frequency signal as an output signal; a first switching circuit for selecting one of a main transmission line and an auxiliary transmission line, and for outputting the output signal of the variable gain circuit to the one of the main transmission line and the auxiliary transmission line; an amplifying circuit provided to the main transmission line, and for amplifying the output signal of the variable gain circuit, which being outputted to the main transmission line; and a directional coupler coupled with the main transmission line with a predetermined amount of coupling, and having one end and another end, wherein the one end of the directional coupler is electrically connected to an auxiliary transmission line, and said another end of the directional coupler is electrically connected to a terminator.
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May 1, 2000
December 24, 2002
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